Deagglomeration of porous siliceous crystalline materials

ABSTRACT

Agglomerated crystalline zeolites are deagglomerated by treating the zeolite following crystallization. At a point where crystallization is complete, a basic solution is added and/or the temperature of the reaction mass is increased by between 50° and 100° F. Alternatively, the crystalline zeolite is recovered and thereafter treated with a basic solution.

NATURE OF INVENTION

This invention relates to the preparation of porous siliceouscrystalline materials. More specifically, it relates to a process forpreparing crystalline zeolite compositions wherein the degree ofagglomeration of the crystals and the dimensions of agglomerates presentare substantially reduced.

BACKGROUND OF THE INVENTION

Highly siliceous porous crystalline materials (zeolite), often looselytermed molecular sieves, are well known in the art. They arecharacterized by their highly ordered crystalline structures and havepores of nearly uniform dimensions. The highly ordered dispersion ofalumina (if present) and silica tetrahedra present in the crystals makefor a large number of active sites and the uniform pore openings of thezeolites allow for easy ingress of certain molecular structures.Processes for producing zeolites synthetically are now well known in theart. For example, U.S. Pat. Nos. 3,702,886 and 3,941,871 (Re. 29,948)disclose a process for synthesizing ZSM-5 zeolite in which the zeolitematerial is crystalized from a reaction mixture of selected reactants.U.S. Pat. No. 3,709,979 discloses a related process for preparing ZSM-11zeolite by crystallization from a reaction mixture. The preparation ofZSM-12 zeolite by crystallization from a reaction mixture is disclosedin U.S. Pat. No. 3,832,449. The preparation of ZSM-23 is disclosed inU.S. Pat. No. 4,076,842. U.S. Pat. No. 4,016,245 discloses thepreparation of ZSM-35 zeolite and U.S. Pat. No. 4,046,859 thepreparation of ZSM-38. The preparation of ZSM-48 zeolite is disclosed inU.S. Pat. Nos. 4,397,827 and 4,375,573.

The entire contents of U.S. Pat. Nos. 3,702,886; 3,941,871 (Re. 29,948);3,709,979; 3,832,449; 4,076,842; 4,016,245; 4,046,859; 4,397,827 and4,375,573 are incorporated herein by reference.

These disclosures in common describe the preparation of zeolites bycrystallizing them from a reaction mixture containing sources of analkali metal oxide, an organic compound, an oxide of aluminum (if addedaluminum is desired), an oxide of silicon, and water.

Often in preparing zeolites for use in commercial operations, such asfixed or fluid bed reactors or adsorption systems, the finely dividedzeolites can be mixed with a binder material such as clay, alumina,silica-alumina, etc. and formed into porous pellets or fluid particles.In order to achieve maximum dispersion and effectiveness of the zeolite,it is desirable that the zeolite crystallites be as fine as possible andmore importantly that they not be agglomerated into relatively largersize particles. Nonagglomerated or deagglomerated crystals are moreeasily dispersed in the compositing medium and a greater amount ofcrystallite surface is exposed for catalytic activity if deagglomeratedcrystals are used.

A primary object of this invention therefore is to prepare poroussiliceous crystalline zeolite materials characterized by a minimumamount of agglomeration of the individual crystallites.

SUMMARY OF THE INVENTION

Briefly stated, this invention constitutes a process for preparingporous siliceous crystalline zeolites wherein sources of an alkali metaloxide, an oxide of aluminum (if desired), an oxide of silicon, anorganic cation and water are combined, a siliceous crystalline materialis crystalized therefrom, and there is added to the crystallizingmixture, or subsequently thereafter, a basic solution such as alkalimetal hydroxide, ammonium hydroxide, or a basic organic compoundsufficient to maintain the pH between 9.0 and 13.5, and preferablybetween 11.5 and 13. The crystalline zeolite is then separated from thecrystallizing mixture. Alternatively, the crystalline siliceous materialformed from the reaction mixture is removed, and subsequently contactedwith the basic solution of alkali metal hydroxide, ammonium hydroxide oran organic base to effect deagglomeration of the crystallite particles.

DESCRIPTION OF THE INVENTION

The porous siliceous crystalline materials are synthesized by preparinga solution containing sources of an alkali metal oxide, preferablysodium oxide, sources of an organic cation, an oxide of aluminum (if theincorporation of aluminum into the zeolite is desired), an oxide ofsilicon and water. The exact temperature and conditions and ratio ofreactants for the particularly desired zeolite is well known to thoseskilled in the art and is not of itself regarded as a novel part of theprocess of this invention.

In preparing certain zeolites, however, particularly those of the ZSM-5type, it is not always desirable to include a source of an oxide ofaluminum. The preparation of these high silica zeolites is described,for example, in U.S. Pat. No. 3,941,871, (Re. 29,948, Mar. 27, 1979),which is incorporated herein by reference.

At a point where crystallization is complete, a basic solution(preferably sodium hydroxide) is added and/or the temperature of thereaction mass is increased by between 50° and 100° F. While maintainingthe reaction mixture at this elevated pH or this elevated temperaturewhich ordinarily will be greater than 150° F., the crystalline zeoliteis separated from the mother liquor for example by filtration. Thecrystalline zeolite recovered is then further treated by washing withwater, ion exchange, drying, calcining, etc.

Alternatively, the crystallization procedure is allowed to go tocompletion and the crystalline zeolite is recovered as by filtering. Therecovered zeolite crystalline mass is then reslurried and treated withthe basic solution at an elevated temperature up to about 100° C., morepreferably from room temperature to 65° C.

For example, a crystalline zeolite such as ZSM-5 can be suitablysynthesized by preparing a solution containing (R₄ N)₂ O, sodium oxide,an oxide of a metal other than a metal of Group IIIA and water andhaving a composition in terms of mole ratios of oxides falling withinthe following ranges:

                  TABLE II                                                        ______________________________________                                                         Broad    Preferred                                           ______________________________________                                        OH.sup.- /SiO.sub.2                                                                              .01-5      .05-1.0                                         R.sub.4 N.sup.+ /(R.sub.4 N.sup.+  + Na.sup.+)                                                   .05-1.0    .1-.8                                           H.sub.2 O/OH.sup.- 50-1000    50-500                                          SiO.sub.2 /M.sub.2/n O                                                                           ≧1  ≧3                                       ______________________________________                                    

wherein R is an alkyl radical, preferably between 2 and 5 carbon atomsand M is total metal. Thereafter, the mixture is maintained untilcrystals of the zeolite are formed. Preferably, crystallization isperformed under pressure in an autoclave or static bomb reactor. Thetemperature ranges from 100° C. to 200° C. generally, but at lowertemperatures, e.g. about 100° C., crystallization time is longer.Typical reaction conditions consist of heating the foregoing reactionmixture to a temperature from about 100° C. to 175° C. for a period oftime of from about 6 hours to 60 days. The more preferred temperaturerange is from about 100° C. to 175° C. with the amount of time at atemperature in such range being from about 12 hours to 30 days.

The treatment of the amorphous mixture is carried out until crystalsform.

The desired ZSM-5 can be prepared utilizing materials which supply theappropriate oxide. Such compositions include sodium silicate, colloidalsilica, silica hydrosol, silica gel, silicic acid, sodium hydroxide,compounds of the desired metal, other than a metal of Group IIIA andtetraalkylammonium compounds, e.g. tetrapropylammonium bromide. Inaddition to tetrapropylammonium compounds, it is contemplated thattetramethyl, tetraethyl or tetrabutyl ammonium compounds may similarlybe employed. It will be understood that each oxide component utilized inthe reaction mixture for preparing the crystalline zeolite of thisinvention can be supplied by one or more initial reactants and they canbe mixed together in any order. For example, sodium oxide can besupplied by an aqueous solution of sodium hydroxide or by an a aqueoussolution of sodium silicate; tetrapropylammonium can be supplied in theform of its hydroxide as can the other tetralkylammonium radicals notedhereinabove. The reaction mixture can be prepared either batchwise orcontinuously. Crystal size and crystallization time of the crystallinecomposition will vary with the nature of the reaction mixture employed.

The crystalline materials thus described are substantially free ofalumina, but may contain very minor amounts of such oxide attributableprimarily to the presence of aluminum impurities in the reactants and/orequipment employed. Thus, the molar ratio of alumina to silica will bein the range of 0 to less than 0.005 Al₂ O₃ to more than 1 mole of SiO₂.Generally, the latter may range from 1 SiO₂ up to 500 or more.

In a similar manner, other crystalline zeolite materials are preparedparticularly those having a constraint index of between 1 and 12 and asilica to alumina ratio greater than 12, more particularly the zeolitesZSM-11, ZSM-12, ZSM-21, ZSM-23, ZSM-35, and ZSM-38.

Although it is preferred to use aqueous solutions of sodium hydroxide asthe washing medium or to add to the crystallizing reaction mixture, thehydroxides of other alkali metals such as potassium, lithium or mixturesthereof can be used. Ammonium hydroxide as well as aqueous solutions ofbasic organic compounds such as amines can also be used.

In the following examples, Examples 1-5 cover the synthesis of andcaustic (NaOH) treatment of Low-Sodium ZSM-5 synthesis by the HydrogelProcedure. Examples 6-10 examine the synthesis of and caustic (NaOH)treatment of High-Solids Low Sodium ZSM-5. In both cases the effect ofthe caustic treatment on the chemical composition and degree of crystalagglomeration is examined. Examples 11 and 12 compare the relativestability of ZSM-5 and amorphous silica gel as a function of causticconcentration, time and temperature. Examples 13-16 show treatment withbasic materials other than sodium hydroxide. Examples 17 and 18 dealwith the use of physical methods for reducing ZSM-5 agglomeratic whileExamples 19 and 20 examine combined chemical and physical treatments.

EXAMPLE 1 Synthesis of Low-Sodium ZSM-5

A sodium silicate solution was prepared by mixing 16 parts water and27.7 parts sodium silicate (28.7 wt. % SiO₂, 8.9 wt. % Na₂ O, 62.4 wt. %H₂ O) followed by addition of 0.08 parts Daxad 27 (W. R. Grace ChemicalDivision). The solution was cooled to approximately 15° C.

An acid solution was prepared by adding 1 part aluminum sulfate (17.2wt. % Al₂ O₃) to 16.4 parts water followed by 2.4 parts sulfuric acid(93 wt. % H₂ SO₄) and 1.2 parts NaCl.

These solutions were mixed in an agitated vessel while 3.9 parts of NaClwere added. The molar matios expressed as oxides were as follows in theresultant mixture:

    SiO.sub.2 /AL.sub.2 O.sub.3 =78.5

    Na.sub.2 O/AL.sub.2 O.sub.3 =49.5

The gel was then heated to about 93° C., agitation was reduced and anorganic solution containing 0.8 parts n-propyl bromide and 1.5 partsmethyl ethyl ketone was added above the gel. After these organics wereadded, 2.3 parts of n-propyl amine was added to the organic phase abovethe gel. This mixture was held at about 93° C. for 6 hours, then severeagitation was resumed. Crystallization was conducted at 93°-99° C. untilthe gel was 80% crystallized, at which time temperature was increased to150°-160° C. Unreacted organics were removed by flashing and theremaining contents cooled. The zeolite slurry product was diluted with4-5 parts water per part slurry and 0.0002 parts of flocculent (Rohm andHaas, Primafloc C-7) per part slurry, and allowed to settle. Supernantliquid was drawn off. The settled solids were reslurried to the originalvolume of the preceeding step with water and 0.00005 parts of flocculentper part slurry. After settling, the aqueous phase was decanted. Thiswas repeated until the sodium level of the zeolite was less than 0.10wt. %. Then 0.1 parts ammonium nitrate per part slurry were added to thesettled solids and the water from the previous decantation. The mixturewas reslurried and the solids were allowed to settle. The washed zeolitesolids were filtered identified as ZSM-5 by X-ray diffraction, andanalyzed as having a SiO₂ /Al₂ O₃ mole ratio of 62.6 and a sodiumcontent of 0.02 wt. % (dry basis).

The detailed chemical analysee are listed in Table 1 along with theresults following mild caustic treatment (Examples 2-5).

EXAMPLES 2-5

To the filtered wetcake from Example 1 was added 1 part deionized waterand 2.1 parts of a 0.42 wt. % NaOH solution per part of filteredwetcake. The treatment was carried out at room temperature for 0, 4, 18and 90 hours for Examples 2-5, respectively. The details of the caustictreatment along with chemical analysis of the treated zeolite andfiltrate are shown in Table 1. The filtrates from these caustictreatments (Examples 2-5) each contained 5-25 times the silicon content(330-1600 ppm Si) as the filtrate from a H₂ O washed zeolite (64 ppmSi), indicating dissolution of some amorphous and/or crystalline SiO₂.The effect of the caustic treatment on crystal agglomeration isillustrated in FIG. 1, a comparison of scanning electron micrographs ofthe low sodium ZSM-5 before (Example 1) and after (Example 4) an 18 hr.caustic treatment at an initial pH of 11.9.

The size and degree of crystal agglomeration was significantly reduced.Note that the low-sodium ZSM-5 of Examples 1-5 was synthesized by thestandard hydrogel technique. The zeolite synthesized in Example 6 whichwas used in Examples 7-10 was prepared using solid silica as the SiO₂source.

EXAMPLE 6

An aluminate solution was prepared by dissolving 11 parts of aluminumsulfate, 15.6 parts of sodium hydroxide and 1 part of ZSM-5 seed (100%solid basis) in 268 parts of water. One hundred and ten parts of Hi-Sil(an amorphous precipitated silica manufactured by PPG Industries) wasthen gradually added to the solution followed by 5 parts of sodiumchloride crystal and 13.3 parts n-propylamine. The mixture was agitatedfor at least 4 hours to obtain a homogeneous slurry. The mixture wasthen heated to 215° F. for approximately 50 hours under constantagitation. The filtered, water-washed and dried solid product had anX-ray crystallinity of 75% based on a specific standard. The detailedchemical analyses are listed in Table 2 along with the results followingcaustic treatment (Examples 7-9).

EXAMPLE 7

To the filtered wetcake of Example 6 was added 1 part deionized waterand 4.20 parts of a 0.42 wt. % NaOH solution per part of filteredwetcake. The treatment was carried out at room temperature for 24 hours.The caustic treated zeolite was then filtered and both the filtrate andthe remaining zeolite were analyzed. The details of the caustictreatment and the chemical analysis results are given in Table 2 alongwith the results from the caustic treatments of Examples 8 and 9.

EXAMPLE 8

Procedure was identical to Example 7 except that a 2 wt. % NaOH solutionwas used for the caustic treatment.

EXAMPLES 9 AND 10

The procedure of Example 9 was identical to Example 7 except that a 10wt. % NaOH solution was used for the caustic treatment. Example 10 is ablank comparison run using deionized water only. The effect of thecaustic treatments on crystal agglomeration is clearly illustrated inFIG. 2, a comparison of scanning electron micrographs of the high-solidslow-sodium ZSM-5 before (Example 6) and after a 24 hour caustictreatment at initial pH's of 11.97, 12.71 and 13.30 (Examples 7-9). Asthe treatment pH increases the degree of agglomeration is reducedsignificantly. In comparison with the low-sodium ZSM-5 synthesized bythe hydrogel procedure (Example 1, FIG. 1) the micrographs indicate thatto reduce crystal agglomeration to a comparable level a higher pH isrequired for the high-solids low-sodium ZSM-5 (Example 6, FIG. 2). Thechemical analyses data of Table 2 indicate increasing Si and Al in thefiltrate as the caustic treatment pH is increased. In addition, the SiO₂/Al₂ O₃ ratio corresponding to the filtrate Si and Al content is 99.3,123.5 and 55.3 for pH's of 11.97, 12.71 and 13.3 (Examples 7-9),respectively. In comparison, the untreated ZSM-5 has a SiO₂ /AL₂ O₃ratio of 53.5. These filtrate chemical analyses indicate that at pH11.97 and 12.71 the material which is dissolved is highlysilicious--possibly amorphous SiO₂, while at pH 13.3 the lower filtrateSiO₂ /Al₂ O₃ ratio suggests dissolution of a portion of the zeolite aswell. This result is also supported by the reduction in the zeolite SiO₂/Al₂ O₃ ratio following the caustic treatments and the apparent reducedX-ray crystallinity of the sample treated at pH 13.3.

EXAMPLE 11

To demonstrate ZSM-5 crystal is more stable than amorphous siliciousmaterial, the following experiment was carried out. The ZSM-5 crystalsof 0.02-0.05μ size range were prepared by the method described inExample 1. The amorphous silica-alumina gel was prepared by the samemethod except no heat was applied. Four grams each of the above threesamples (based on 100% solids) were treated with 100 ml of H₂ O, 0.1N,0.2N, 0.5N and 1.0N of NaOH solution respectively at 100° C. for aperiod of 1 hour. The remaining solid after the treatment was separatedfrom the solution using a centrifuge. The weight of washed and driedsamples were plotted against the concentration of the caustic solutionsin FIG. 3. The solubility of amorphous silica gel and Hi-Sil is muchgreater than crystalline ZSM-5.

EXAMPLE 12

The ZSM-5 crystal and silica amorphous gel described in Example 11 weretreated in four gram samples with 100 ml of 0.5N NaOH at 25° C. and 100°C. for 1 hour, 2 hours, 4 hours, 8 hours, 24 hours and 72 hours. Theundissolved solid was separated from caustic solution by centrifugeafter treatment. The result is plotted in FIG. 4. Amorphous silica gelwas more soluble at both temperatures. The weight of undissolved solidstabilized after about 2 hours.

                  TABLE 1                                                         ______________________________________                                        Effect of Caustic Treatment on the Chemical Composition                       of Low Sodium ZSM-5                                                                      Example Number                                                                1    2      3        4      5                                      ______________________________________                                        Treatment Conditions:                                                         Wt. of Reagents, gm                                                           Zeolite Wetcake                                                                            --     200    200    200    200                                  Deionized H.sub.2 O                                                                        --     200    200    200    200                                  NaOH Soln    --     420    420    420    420                                  (0.42 wt %)                                                                   Treatment Temp, °F.                                                                 --     R.T.   R.T.   R.T.   R.T.                                 Treatment Time, hrs.                                                                       --      0      4      18     90                                  Filtrate Analysis                                                             pH           --     11.88  11.0   10.87  9.89                                 Al, ppm      --     --      34     20     33                                  Si, ppm      --     --     685    1600   330                                  Na, ppm      --     --     880    --     1100                                 Low-Sodium ZSM-5                                                              Analysis                                                                      Wt. %: SiO.sub.2                                                                           81.2   --     87.6   84.0   88.8                                 Al.sub.2 O.sub.3                                                                           2.20   --      2.3    2.2    2.8                                 C            4.77   --     5.56   6.17   5.83                                 N            1.36   --     1.23   1.50   1.36                                 Na           0.02   --     <0.09  <0.09  <.05                                 Ash          86.4   --     91.3   89.2   91.1                                 Mole Ratios                                                                   SiO.sub.2    62.6   --     64.6   64.8   53.8                                 Al.sub.2 O.sub.3                                                                           1      --      1      1      1                                   C            18.4   --     20.54  23.8   17.7                                 N            4.50   --     3.89   4.97   3.54                                 Na           0.04   --     <.17   <.17   <.08                                 C/N          4.09   --     5.28   4.79    5.0                                 ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Effect of Caustic Treatment on the                                            Chemical Composition of High-Solids Low-Sodium ZSM-5                                     Example Number                                                                6    7       8        9     10                                     ______________________________________                                        Treatment Conditions:                                                         Wt. of Reagents, gms                                                          Zeolite Wetcake(1)                                                                         --     50      50     50    50                                   Deionized H.sub.2 O                                                                        --     50      50     50    260                                  NaOH Soln    --     210     210    210   --                                                       (0.42   (2 wt. %)                                                                            (10                                                            wt. %)         wt. %)                                     Treatment Temp, °F.                                                                 --     R.T.    R.T.   R.T.  R.T.                                 Treatment Time, hrs.                                                                       --     24      24     24    24                                   Initial Slurry pH                                                                          --     11.97   12.71  13.30 8.87                                 Filtrate Analysis                                                             pH           --     10.87   12.34  13.13 8.46                                 Al, ppm      --     31      53     390   <1                                   Si, ppm      --     1600    3400   11200 80                                   Na, ppm      --     0.13    0.58   2.74  0.026                                Low-Sodium ZSM-5                                                              Analysis                                                                      Wt. %: SiO.sub.2                                                                           85.2   86.4    85.2   84.0  86.4                                 Al.sub.2 O.sub.3                                                                           2.7    2.9     3.1    3.0   2.8                                  C            5.30   5.47    5.40   5.37  5.31                                 N            1.97   1.83    1.89   --    1.96                                 Na           0.39   <.05    0.15   2.20  <0.05                                Ash          90.5   90.5    90.4   88.1  90.5                                 Mole Ratios                                                                   SiO.sub.2    53.5   50.6    46.6   47.5  52.4                                 Al.sub.2 O.sub.3                                                                            1      1       1      1     1                                   C            16.7   16.0    14.8   15.2  16.1                                 N            5.31   4.60    4.44   --    5.10                                 Na           0.64   <0.08   0.21   3.25  <.08                                 C/N          3.15   3.48    3.33   --    3.16                                 X-ray Crystallinity (2)                                                                    75     75      80     65    75                                   ______________________________________                                         (1) 36 weight % solids                                                        (2) Based on a specific standard                                         

EXAMPLE 13-16 Treating ZSM-5 with Basic Materials Other Than SodiumHydroxide

ZSM-5 (synthesized as in Example 6) was treated with sodium aluminatesolutions of varied concentrations similar to the caustic treatmentsdescribed previously. The pH of these solutions were similar to theforementioned caustic solutions. Table 3 lists the conditions andresults of these treatments. Within the pH range used in the sodiumhydroxide experiments, the sodium aluminate solutions do not appear tobe effective in reducing agglomeration. As noted in the silica toalumina ratio of the filtered product, much of the alumina remains withthe zeolite after treatment. Furthermore the level of crystallinitydecreased with increasing both time and/or severity of treatment. FIG. 5(Examples 13-16) supports the conclusions that no reduction in zeoliteagglomeration took place in the sodium aluminate treatments.

                                      TABLE 3                                     __________________________________________________________________________         Weight %                                                                            Normality                                                                           Total                                                                             pH    pH           Silica to                             Example                                                                            Zeolite in                                                                          of    Mixing                                                                            Before                                                                              After %      alumina                               Number                                                                             Solution                                                                            NaAlO.sub.2                                                                         Time                                                                              Treatment                                                                           Treatment                                                                           Crystallinity                                                                        Ratio                                 __________________________________________________________________________     6                               75     53.5                                  13   11    3      4  12.8  13.6  50     5                                     14   11    3     24  12.8  13.4  35     4                                     15   11    0.75   4  11.7  12.1  65     13                                    16   11    0.75  24  11.7  12.1  65     13                                    __________________________________________________________________________

EXAMPLES 17 AND 18

ZSM-5 wetcake (refer to Example 6) was added to water to a solidscontent of approximately 19%. This mixture was stired until homogeneousand then subjected to a four hour high speed mixing on a CowlesDissolver Model W-24 at 1600 rpm. Example 17 (FIG. 6) shows that thehigh speed mixing did not reduce the extent of zeolite agglomerationsomewhat but not to the extent of the previously described sodiumhydroxide treatments.

An equivalent zeolite mixture was prepared and processed through aGaulin Homogenizer at 1000 psig twice and the filtered. Example 18 (FIG.6) shows that this type of physical treatment did little to reduce thezeolite agglomeration.

EXAMPLES 19 AND 20

ZSM-5 wetcake (refer to Example 6) was added to water to a solidscontent of approximately 22%. To this mixture enough (2% wt.) sodiumhydroxide was added to reduce the solids content to 11%. The pH of thissolution was 12.7. This solution was mixed for 2 hours before a samplewas taken, filtered and dried. Example 19 (FIG. 7) shows that as claimedpreviously the mild caustic treatment did reduce the zeoliteagglomeration. To the remaining solution additional 2% (wt.) sodiumhydroxide was added to reduce the solids content to 5.5%. The pH of thissolution was 12.9. This solution was subjected to two hours of highspeed mixing by a Cowles Dissolver Model W-24 at 1600 rpm before asample was taken, filtered and dried. Example 20 (FIG. 7) illustratesthat there was little improvement resulting from the high speed mixingcompared to the caustic treatment (Example 19). These results indicatethat any improvement in reducing zeolite agglomeration caused byphysical treatments is insignificant compared to the chemicaltreatments.

What is claimed is:
 1. In a method for preparing a porous crystallinezeolite wherein a mixture containing sources of an alkali metal oxide,an oxide of silicon, an organic cation and water in predetermined ratiosis maintained at a predetermined temperature until said zeolite iscrystallized and said zeolite is subsequently separated from saidmixture, the improvement comprising after crystallization is completeincreasing the temperature of said mixture by an increase of betweenabout 50° and about 100° F. for a period of time sufficient to effectdeagglomeration of said zeolite prior to separating said crystallizedzeolite from said mixture.
 2. The method of claim 1 wherein said mixturealso contains a source of aluminum oxide.
 3. The method of claim 1wherein said zeolite is ZSM-5.
 4. The method of claim 1 wherein saidzeolite is ZSM-11.
 5. The method of claim 1 wherein said zeolite isZSM-12.
 6. The method of claim 1 wherein said zeolite is ZSM-23.
 7. Themethod of claim 1 wherein said zeolite is ZSM-35.
 8. The method of claim1 wherein said zeolite is ZSM-38.
 9. The method of claim 1 wherein themixture is maintained at the temperature increase of about 50° to about100° F. for a time period of about 6 hours to about 60 days.